Torsion damper for hybrid electric transmission

ABSTRACT

A vehicle powertrain includes an engine, a torsion damper connected to the engine, a torque converter, a housing enclosing a clutch, a motor and gearing, and a drive shell surrounding the torque converter, including an input connected to the damper, an output connected to the clutch, the clutch and the motor located between the torque converter and the gearing, the torsion damper located between the engine and the torque converter.

This application is a continuation-in-part of pending U.S. applicationSer. No. 13/271,044, filed Oct. 11, 2011.

TECHNICAL FIELD

This invention relates to the powertrain of a hybrid electric vehicle,particularly to a torsion damper located in a torque delivery pathbetween an engine and a torque converter.

BACKGROUND

Hybrid electric vehicles (HEVs) have both an internal combustion engineand an electric motor which can alternately or in combination be used topropel the vehicle. A variety of different drive trains are used inhybrid vehicles. The present application relates to a parallelconfiguration in which the engine is connected to the motor by adisconnect clutch with the motor driving the torque converter input ofan automatic hydraulic transmission. The hydraulic transmission has anoutput which is connected to a differential coupled to the two drivenwheels of the vehicle. This parallel hybrid electric vehicle drive chainpower flow arrangement is known in the art.

A problem facing HEV designers is how to cool the disconnect clutch andthe rotor and stator portions of the electric motor. Various air andliquid based cooling systems have been proposed; however, most systemsare costly and pose packaging problems when trying to convert anon-hybrid vehicle to a hybrid operation. A need exists to package thedisconnect clutch, motor, torque converter and automatic transmission ina compact manner so that a conventional vehicle can be reconfigured as ahybrid at a relatively low cost and with little or no vehicle bodymodifications.

SUMMARY

A vehicle powertrain includes an engine, a torsion damper connected tothe engine, a torque converter, a housing enclosing a clutch, a motorand gearing, and a drive shell surrounding the torque converter,including an input connected to the damper, an output connected to theclutch, the clutch and the motor located between the torque converterand the gearing, the torsion damper located between the engine and thetorque converter.

The present invention relates to a novel hybrid electric vehicle as wellas a number of novel components and subcomponents specifically adaptedto reorient the disconnect clutch and the electric motor within the wetside of the automatic transmission. This is done without changing theconventional power flow in which the engine, disconnect clutch, motor,torque converter, transmission are connected in series.

Rather than connect the torque converter directly to the engine as istypically done in a non-hybrid vehicle, a drive shell is provided whichconnects the engine to the input side of the disconnect clutch which ishas been relocated into the automatic transmission housing. The driveshell forms an annular cavity of sufficient size to contain the torqueconverter freely therein. The motor is also located in the automatictransmission wet zone preferably circumaxially surrounding thedisconnect clutch. The rotor of the motor is connected to the disconnectclutch output. The disconnect clutch output and the rotor are bothcoupled to the rotor shaft which is connected to input turbine of thetorque converter. The torque converter stator and the output turbine areconnected to a tubular stator shaft and a transmission input shaftrespectively. The transmission input shaft, the stator shaft, the rotorshaft and the disconnect clutch hub are all concentric with one anotherand accessible through an annular opening in the front side of theautomatic transmission housing.

The torque converter and the drive shell are removably mountable on thefront of the transmission housing similar to a conventional torqueconverter. Rather than attaching the torque converter to the enginemounting plate, a drive shell is attached to the mounting plate. Thetorque converter is free to rotate relative to the drive shell withinthe drive shell cavity, resulting in a compact and axially shortmotor/transmission assembly. By locating the disconnect clutch and motorcoaxially in the front portion of the wet zone of the automatictransmission, the transmission hydraulic fluid pump, associated pump andplumbing system can cool the disconnect clutch and the rotor and statorportions of the electric motor with relatively little increase in axiallength.

The torque converter, while generally similar to a conventional torqueconverter, is uniquely adapted in order to practice the invention. Sincethe torque converter is not attached to the engine mounting plate, nomounting studs are provided on the shell of the torque converter.Rather, a central axially bearing member is provided which cooperateswith an engine mounting plate provided with a corresponding bearingmember in order to radially support the torque converter and limitaxially movement in the forward direction. Within the torque converteris a rearward facing thrust bearing member which cooperates with thefree end of the transmission input shaft to limit the axial movement ofthe torque converter in the rearward direction.

The transmission housing is preferably also uniquely adapted in order topractice the present invention. The transmission housing includes a wethousing which partially defines an enclosed wet zone and a torqueconverter housing, adapted to be affixed to the wet housing on one sideand to the engine block on the other. The torque converter housing has arear wall which forms a boundary between the wet cavity and the drycavity in which the torque converter and drive shell are oriented. Therear wall defines an annular bore which cooperates with the disconnectclutch input hub to support the input hub and the rotor shaft along withthe associated rotor portion of the motor and the disconnect clutchoutput hub.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a hybrid electric vehicle having aparallel-flow design;

FIG. 2 is a simplified schematic illustration of the disconnect clutchand motor reoriented in the present invention;

FIG. 3 is a simplified cross-sectional view of an automaticmotor/transmission assembly of the present invention;

FIG. 4a is a more detailed cross-sectional side elevation view of anautomatic motor/transmission assembly of the present invention;

FIG. 4b is a stick diagram of the motor/transmission assembly of FIG. 4a;

FIG. 4c is a clutch application schedule for each of the six forwardgears and reverse;

FIG. 5 is an enlarged view of the cross-section of the torque converterin its cooperation with the disconnect clutch and motor;

FIG. 6 is an enlarged view of the disconnect clutch and electric motor;

FIG. 7 is an enlarged view of the engine output on the mounting platetorque converter and the transmission input shaft showing their axialorientation;

FIG. 8 is a perspective view of a mounting plate used to practice thepresent invention;

FIG. 9 is a perspective view of a torque converter used to practice thepresent invention;

FIG. 10 is a perspective view of a drive shell;

FIG. 11 is a view of an alternative embodiment of the drive shell with atorque inverter entrapped therein;

FIG. 12 is side cross-sectional view of the portion of the vehiclepowertrain located above the central axis;

FIG. 13 is top view of a terminal block assembly;

FIG. 14 is side cross-sectional view of a portion of the vehiclepowertrain located below the central axis;

FIG. 15 is side cross-sectional view above the central axis of vehiclepowertrain showing a torsion damper located between the engine andtorque converter.

DETAILED DESCRIPTION

FIG. 1 illustrates a hybrid electric vehicle 10 schematically shown witha parallel type hybrid electric drive train. The hybrid electric vehicleis provided with an engine 12 having a rotary output which is connectedto a disconnect clutch 14 which drives an electric motor 16. The outputof the electric motor is connected to the input of torque converter 18,the output of which is connected to the input shaft of automatictransmission 20. In a conventional manner, the automatic transmission isconnected to the driven wheels, 22, 22′ by a differential 24. In theschematic illustration, hybrid electric vehicle 10 is provided with apair of non-driven wheels, however, alternatively, a transfer case and asecond differential can be utilized in order to positively drive all ofthe vehicle's wheels. The engine, disconnect clutch, motor, torqueconverter and the automatic transmission are connected sequentially inseries, as illustrated in FIG. 1.

Motor/transmission assembly 26, in hybrid electric vehicle 10′,schematically illustrated in FIG. 2, repackages the drive componentswhile maintaining the same power flow, as shown in FIG. 1. Engine 12 ismechanically connected to the input side above disconnect clutch 14 viaa drive shell 28 which forms an annular chamber sufficiently large toextend about torque converter 18. The output of disconnect clutch 14 isconnected to electric motor 16 which, in turn, is connected to theImpeller “I” of torque converter 18. The use of the drive shell 28enables the disconnect clutch and motor to be positioned within the wetside of the automatic transmission housing. Turbine “T” is attached tothe output of torque converter 18 which is connected to the input shaftof the automatic transmission in a conventional manner. The inventioncan be practiced with a wide variety of automatic transmissions. Thepreferred embodiment of the transmissions described herein is asix-speed, three planetary gear set, five clutch design; alternativetransmission structures having fewer or greater speeds and differentmechanical configurations can likewise be benefited from the presentinvention.

A more detailed, yet quite simplified illustration of themotor/transmission assembly 26 is shown in FIG. 3. The engine isprovided with a crank shaft output flange 30 which is bolted to mountingplate 32 in a conventional manner. The mounting plate 32, rather thanattaching to the shell of the torque converter, is affixed to the driveshell 28 which has sufficient diameter to encircle the torque converterand connect to the input hub 34 of disconnect clutch 14. The output ofthe disconnect clutch is affixed to the rotor “R” portion of motor 16and in turn, is connected to rotor shaft 36. The rotor shaft 36 iscoaxially nested within the disconnect clutch input hub 34 and extendsto an annular opening in the wall portion of the transmission housingdefining the wet zone of the transmission. Rotor shaft 36 is connectedto the impeller “I” of torque converter 18, which in turn drives turbineT connected to transmission input shaft 38. Coaxially spaced between theinside diameter of rotor shaft 36 and the periphery of the transmissioninput shaft 38 is a stator shaft 40 which is fixed relative to thetransmission housing and supports stator element S located within torqueconverter 18.

Preferably, the case of the motor/transmission assembly is made up of awet housing 42 which partially defines the enclosed wet zone cavity, anda torque converter housing 44 which is adapted to be affixed to the wethousing 42 and to the engine block 46. The torque converter housing 44is preferably provided with rear wall 48 having an annular axial opening50 on the transmission centerline. Rear wall 48 forms a physicalboundary between the wet zone cavity and a dry cavity in thetransmission housing. The torque converter 18 and drive shell 28 arelocated in the dry zone as shown. Rear wall 48 cooperates withdisconnect clutch input hub 34 which in turn supports motor rotor shaft36 and the associated rotor portion R of motor 16.

The motor/transmission assembly is provided with pump P for hydraulicfluid oriented within the wet zone of the transmission housing anddriven by the rotor shaft 36. Pump P provides pressurized hydraulicfluid to operate the clutches and brakes within the transmission drivetrain as well as operating the disconnect clutch and provides coolingfor the clutches and motor 16. Similarly, the disconnect clutch andmotor share a common sump 52 for transmission fluid as well as a commonpump screen 54. Automatic transmission 20 is provided with an outputshaft 56. FIG. 4a is a cross-sectional side elevational view of themotor/transmission assembly 26. Once again, the present invention can beutilized with a number of different transmission gear trainconfigurations and is not limited to the disclosed six-speed, threeplanetary gear set transmission.

The preferred embodiment of the multi-speed transmission shown in FIG.4a is more easily understood with reference to the stick diagram of FIG.4b . The input from the engine drives mounting plate 32 which isfastened to drive shell 28 connected to input hub 34 of disconnectclutch 14. The output side of disconnect clutch 14 is connected to therotor portion of motor 16, which in turn is attached to rotor shaft 36.Coaxially oriented within rotor shaft 36 is a fixed stator shaft 40which is mounted to the transmission case, and the transmission inputshaft 38. The torque converter impeller I drives torque converterturbine T which is connected to transmission input shaft 38. The torqueconverter 18 is further provided with a stator S mounted on the statorshaft 40, by way of a one-way clutch 56. In the preferred embodimentillustrated, torque converter 18 is further provided with a lock upclutch 58 which locks the turbine to the impeller in a well knownmanner.

The gear set of the planetary automatic transmission 20 is made up ofthree planetary stages; plan 1, plan 2 and plan 3, which are coaxiallyaligned and axially spaced as shown. Each planetary gear set has a sun,a ring and a series of plant gears supported on a planet carrier. Thesun, ring and planet carrier members can be interconnected via a seriesof five clutches and brakes. For example, in first gear, clutch A andbrake D are engaged as illustrated in clutch application table in FIG.4c . The transmission input shaft 38 is connected to the ring ofplanetary gear set Plan 1. The sun is fixed and the planet carrier isconnected via clutch A to the sun of planetary gear set 3. With clutch Dengaged, the planet carrier of planetary gear set 3 is fixed causing thering gear of planetary gear set 3 to drive the transmission output shaft56. In order to shift to the second gear, brake D is released and brakeC is simultaneously engaged to cause a change in the transmission gearratio. Each shift, either up or down, is achieved by releasing oneclutch or brake and engaging another. Similarly, the shift from firstreverse is done by a single clutch release, a simultaneous engagement ofanother clutch.

Planetary gear sets 2 and 3 share a common planet element as well as acommon ring gear. Planetary gear sets 1 and 2 are traditional, simpleplanetary gear sets, while planetary gear set 3 is a compound planetarygear set having a pair of inter-meshed planets, one engaging the sun andone engaging the ring. In the embodiment illustrated in FIG. 4b , thecompound planet arrangement enables the third planetary gear set to usea smaller sun and accordingly, obtain a higher gear reduction ratio.Again, the planetary gear set is described merely to illustrate thepreferred embodiment, however, the invention can be practiced with awide variety of automatic transmission structures.

FIG. 5 is a cross-sectional view illustrating an alternative drive shellarrangement 62 which is designed to accommodate a smaller diametermounting plate 64. Output flange 30 of the engine crank shaft isattached to mounting plate 64 by a series of bolts extending through anarray of holes in the mounting plate spaced from the mounting platecenter. The outer peripheral edge of mounting plate 64 is provided witha ring gear 66 for cooperation with the pinion gear of the startermotor. Inboard of the periphery of the mounting plate is a series ofholes sized to receive threaded fasteners for connecting the drive shell62 to the mounting plate 64. In the embodiment illustrated, the driveshell 62 is provided with threaded studs 108 which project through anarray of holes in the mounting plate 64 to receive nuts to securelyaffix the drive shell to the mounting plate. Nuts alternatively could bewelded to the mounting plate to receive bolts passing through theapertures in the mounting plate. The mounting plate alternatively mayalso include a dual mass damper (not shown) in order to reduce torquefluctuations.

Unlike a conventional automatic transmission vehicle, the torqueconverter 18 is not bolted to the engine mounting plate, rather it isfree to rotate within the annular cavity defined by the drive shell 62and mounting plate 64. The rearward end of the drive shell forms atubular drive shell outlet member 68 which is connected to disconnectclutch input hub 34. Rearward refers to the direction toward thetransmission output shaft 56 which would be to the rear of a vehicle ina traditional rear wheel drive front engine vehicle, however, the terms,“rearward” and “forward” are used for simplicity and explanationpurposes. They do not necessarily refer to the front and rear of thevehicle as would not be the case if installed transversely in a frontwheel drive vehicle. The forward side of the torque converter 18 is freeof studs typically used to attach to the mounting plate.

Preferably, the drive shell tubular output hub 68 is provided with aninternal spline to axially cooperate with a complimentary externalspline on disconnect clutch input hub 34. Disconnect clutch 14 has aseries of inter-leaved plates alternatively connected to the input hub34 and output hub 70. A disconnect hub ring shape piston 72 cooperateswithin a corresponding cavity formed in the disconnect clutch output hub70 and is axially shiftable between an extended locked position when thehydraulic signal advancing the disconnect clutch piston 72 is received,and a retracted position when the signal is not present. Affixed to theouter periphery of the disconnect clutch output hub 70 is the rotor R.Disconnect clutch output hub 70 and rotor R are both mounted on andsecured to rotor shaft 36. Rotor shaft 36 is provided with externalspline sized to cooperate with a complimentary internal spline on thetorque converter input hub 74 which drives impeller I. Torque converter18 is further provided with a stator S mounted on a stator hub 76 and anoutput turbine T which is connected to turbine output hub 78 via atorsional damper 82 illustrated in FIG. 5. Turbine output hub 78 isprovided with an internal spline cooperating with transmission inputshaft 38. Stator hub 76 is mounted on stator shaft 40 which is affixedto and extends out of the transmission housing. In the embodimentillustrated, the stator is mounted on a one-way clutch center in aconventional manner.

The torque converter 18 and drive shell 62 together mate with the fourdifferent coaxial aligned members in the transmission and slide on andoff during installation like a conventional torque converter in anautomatic transmission, simply having one additional coaxial member, thetubular output 68 of the drive shell 62. Accordingly, the use of thedrive shell takes very little additional axial space in themotor/transmission assembly. The addition of the disconnect clutch 14and motor 16 to the transmission, however, does take some additionalaxial space inside of the transmission housing. As shown in FIG. 6, themotor is oriented coaxially with the disconnect clutch mounted inside ofmotor rotor R. Motor stator S is securely affixed to the transmissionhousing by a series of annularly spaced apart bolts which extend throughthe stator laminate stack. The motor rotor R is mounted to the outerperiphery of the disconnect clutch output hub 70 supported on rotorshaft 36.

The rotor shaft 36 is radially located by a roller bearing 80 interposedbetween the rotor shaft 36 and disconnect input clutch hub 34. Theoutside diameter of the disconnect clutch input hub is supported upon awall 48 in the transmission housing by way of a bearing 84. Bearing 84is designed to take an axial load as well as the radially load insertedby the rotor disconnect clutch output hub assembly. A disconnect clutchoutput hub 70 is further axially constrained by thrust bearings 86 and88. Additionally, a circumaxial roller bearing 90 is interposed betweenthe disconnect clutch output hub 70 and stator shaft 40 to axiallylocate rotor shaft 36 and the associated disconnect clutch and rotor.

The disconnect clutch output hub 70 is provided with internal coolantpassageways 92 which feed transmission fluid through the disconnectclutch output hub into the rotor R. As fluid passes through and exitsthe rotating rotor R, it strikes the windings of stator S to removeexcess heat from stator windings and the associated stator laminatestack. As illustrated in FIG. 6, disconnect clutch output hub 70 is alsoprovided with an output spline 94 for driving pump P.

Since the torque converter 18 is no longer affixed to the enginemounting plate, it is necessary to axially and radially constrain thetorque converter. The torque converter 18 is pivotally supported on theengine mounting plates 32 and 64 in FIGS. 3 and 5. The engine mountingplates 32, 64 are provided with an axially mounted first bearing member96 which cooperates with a mating second bearing member on the torqueconverter 18. As illustrated in FIG. 7, the first bearing member in thepreferred embodiment is provided by a roller bearing 96 supported in abearing cup 98 affixed to the mounting plate on the transmissioncenterline. The corresponding second bearing member is provided by astub shaft 100 which is affixed to the shell of torque converter 18. Thestub shaft provides radial support for the torque converter whilebearing 96 further provides an axial stop for the torque converter inthe forward direction. To limit rearward movement of the torqueconverter, the torque converter is provided with a thrust bearing 102 onthe axial center line of the shell interior facing rearward for engagingthe end region of the transmission input shaft 38. Of course,alternative structures can be utilized such as placing the stub shaft onthe mounting plate and the roller bearing on the torque converter shell.

The motor/transmission assembly 26, as previously described, uses anumber of subcomponents which are independently novel. FIG. 8 is aperspective view of the mounting plate 64 formed of a circular discprovided with a centrally axially aligned first bearing member, rollerbearing 96, mounted in bearing cup 98. The disc is provided with twocircular arrays of mounting holes, an array adjacent the center toattach to the crankshaft of the engine and an array adjacent theperiphery to attach to the drive shell 28.

Torque converter 18, illustrated in FIG. 9, is similarly novel. Thetorque converter outer shell is not provided with the conventionalmounting studs, rather it is provided with a central axial secondbearing member, which in this case is provided by a stub shaft 100.Other axial central bearing members could alternatively be used providedthat they cooperate with a corresponding bearing structure on themounting plate to bear radial loads and provide a positive forward stopfor torque converter movement. The torque converter has an annularrearward facing tubular outlet hub 68 which connects to rotor shaft 36,and a rearward facing thrust bearing 102 on the centerline inside of theshell as show in FIG. 7 to abut the end of transmission input shaft 38.

FIG. 10 illustrates a perspective view of a drive shell 28. The driveshell is an annular member having an outer peripheral structuresufficiently large to freely surround the torque converter. The forwardedge of the drive shell 28 is provided with a series of spaced apartfasteners 104 for cooperation with the mounting plate 32. The rearwardend of the drive shell forms a tubular output 68 which preferably has asplined internal diameter for engaging a corresponding spline on thedisconnect clutch input hub 34. The spaced apart fasteners 104illustrated are a series of weld studs, however weld nuts could also beused to cooperate with bolts passed through corresponding apertures inthe mounting plate.

FIG. 11 illustrates an alternative drive shell embodiment 62 aspreviously illustrated in FIG. 5. In order to accommodate a smalldiameter mounting plate and a relatively large torque converter, thedrive shell is provided with a series of inwardly projecting radialmembers 106 supporting fasteners The illustrated fasteners are providedby studs 108 located at the diameter of the array of holes in themounting plate which is significantly less than the diameter of thetorque converter. As a result, the inwardly projecting members 106entrap the torque converter 18 inside the large annular cavity formedwithin the drive shell 62 creating the illustrated drive shell torqueconverter sub assembly.

Referring to FIG. 12, disconnect clutch 14 further includes a blockerring 110, secured against axial displacement relative to output hub 70;a balance dam 112, also secured against axial displacement relative tooutput hub 70; a return spring 114, contacting piston 72 and balance dam112 at opposite ends of the spring; and a sealed hydraulic cylinder 116,in which the piston moves subject to the force of spring 114 and apressure force. A hydraulic passage 118 carries actuating pressure froman outlet port 120 of a pump housing 122 through an axial passage 123 tothe portion of cylinder 116 located behind piston 72. When pressure inpassage 118 is high, piston 72 moves axially leftward against the forceof spring 114 forcing the friction plates and spacer plates of clutch 14unto mutually frictional contact, thereby engaging clutch 14.

An axial hydraulic passage 124 carries fluid from pump housing 122through passage 126 to the portion of cylinder 116 that is locatedbetween piston 72 and balance dam 112. Hydraulic passage 124 alsocarries fluid from pump housing 122 through radial passage 92 to therotor R and stator S of motor 16. Passage 92 communicates with passages128, which direct fluid across the width of motor 16 and onto thesurfaces of rotor R. Fluid exiting the rotor flows radially outward atopposite axial sides due to centrifugal force and onto the surface ofthe stator S. This fluid, which carries heat away from the motor 16,flows downward though an opening 129 (shown in FIG. 14) in the housing42 and returns to the sump 52.

Hydraulic fluid that fills the torque converter 18 is carried from pumpP through radial passage 130 and axial passage 132, which is located inan annular space between stator shaft 40 and the transmission inputshaft 38. The forward end of passage 132 communicates through a radialpassage 134 with the toroidal chamber of the torque converter, which issurrounded by the shroud 136 and contains the impeller I, turbine T andstator S. Hydraulic fluid exiting torque converter 18 is carried throughan axial passage 138 formed in the transmission input shaft 38 andextending along axis 140.

As FIG. 12 shows, the motor's stator S is secured by a series of bolts150 to the transmission case 42, which is formed with an opening 152.Each bolt 150 passes though a hole formed in the stator S, and thethreaded shank of each bolt engages a threaded hole formed in the casing42. Close dimensional tolerances are established among the lower surface153 of stator S, the centerline through the hole in stator S and bolts150, and the location of axis 140. In this way the distance between axis140 and the lower surface 153 of stator S is established within a closedimensional tolerance in order to establish and maintain a narrow airgap between the motor's stator S and rotor R.

A terminal assembly 154, seated on a mounting surface 156 that surroundsthe opening 152, includes a block 157 that contains electric terminals158 including at least one high voltage terminal that is electricallyconnected to the windings within laminates 160 of the motor's stator S.Each terminal 158 is connected by a bolt 162, whose shank passes througha plate 164, which is secured by bolts 166 to the transmission case 42.Each bolt 162 also electrically connects and secures each terminal 158to a receptacle 168, which engages a conductor 170 connected to thestator S. Both receptacle 168 and conductor are elastically flexible inflexure such that their connection to stator S is completed andmaintained without substantially altering the distance between surface153 and axis 140.

The terminal block assembly 154 is preferably located at an angularlocation relative to axis 140 that places the terminals 158 at a lateralside of the transmission case 42, rather than at the higher elevationshown in FIG. 12. Preferably the terminals 158 are directed along axis140, although not necessarily parallel to the axis, and the receptaclesof the terminals face rearward, as FIG. 13 shows.

The rotor R of motor 16 is secured to output hub 70 such that an air gaplocated between the stator's reference surface 153 and the radial outersurface 176 of the rotor is established.

As FIG. 14 shows housing 44 is secured by a series of bolts 177 to thetransmission housing 42. The pump's centering plate P is guided into itscorrect position, both radial and axial, due to contact between surface178 on the pump's centering plate P and a pilot surface 180 on thetransmission housing 42. Similarly pump housing 122 is guide into itscorrect position, due to contact between surface 182 on the pumpcentering plate P and a surface 184 on the pump housing 122. At therearward end, the outer surface of stator shaft 40 contacts the radialinner surface of pump centering plate P, and at the forward end theouter surface of stator shaft 40 contacts the radial inner surface ofthe torque converter input hub 74.

The axial and radial location of bearing 84 is established by itscontact with the rear wall 48 of housing 44. The axial and radiallocation of clutch input hub 34 is established by its contact withbearing 84. The position of the forward end of rotor shaft 36 isestablished by its contact with roller bearing 80, and the position ofthe rearward end of rotor shaft 36 is established by its contact withthe inner surface of pump housing 122.

The position of the forward end of output hub 70 and rotor R isestablished by contact between the outer surface of rotor shaft 36 andthe inner surface of output hub 70. The axial and radial location ofbearing 190 is established by its contact with the pump housing 122. Theposition of the rearward end of output hub 70 and rotor R areestablished by contact between bearing 190 and the output hub 70.

In this way the radial position of the radial outer surface 176 of therotor R of motor 16 is located such that the air gap parallel to aradius extending from axis 140 and located between the stator'sreference surface 153 and the radial outer surface 176 of the rotor ispreferably about 122 mm.

FIG. 15 shows a torsion damper 196 located in a power path between theengine 12 and the drive shell 28, 62. Engine 12 is connected throughcrankshaft flange 30 to an input of damper 196, and a series of bolts108, spaced mutually around axis 140, connect the output of damper 196to drive shell 28, 62. Damper 196 attenuates torsional vibrationsproduced by the engine. The outer peripheral edge of damper 196 isprovided with a ring gear 66, which is engaged by a pinion gear drivenin rotation by a starter motor.

FIG. 15 shows damper 196 arranged in series with damper 82 betweenengine 12 and transmission input shaft 38. The presence of damper 196 inthe powertrain may eliminate need for torsion damper 82, which islocated in a torque delivery path of torque converter 18 between theimpeller shroud 136 and the turbine hub 78. When damper 82 iseliminated, the axial dimension of the torque converter 18 and driveshell 28, 62 can be reduced.

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

What is claimed is:
 1. A vehicle powertrain comprising: an engine; atorsion damper connected to the engine; a torque converter having animpeller shroud; a housing enclosing a clutch, a motor and gearing; adrive shell surrounding the impeller shroud, including an inputconnected to the damper, an output connected to the clutch, the clutchand the motor located between the torque converter and the gearing, thedamper located between the engine and the torque converter; wherein thedrive shell is rotatable independently from the torque converter whenthe clutch is disengaged, and the drive shell is rotationally coupled tothe torque converter when the clutch is engaged.
 2. The powertrain ofclaim 1 wherein the torque converter is provided with an input shaftconnected between the motor and an impeller of the torque converter, astator mounted on a stator shaft secured to the housing, and a turbinemounted on an input shaft of the gearing.
 3. The powertrain of claim 2,wherein the torque converter includes the impeller, and a second torsiondamper located in the impeller shroud and in a power path between theimpeller and the input shaft of the gearing.
 4. The powertrain of claim2 wherein the input shaft of the gearing, the stator shaft, and thetorque converter input shaft are arranged coaxially with the drive shelloutput.
 5. The powertrain of claim 1 wherein the torque converterincludes a thrust bearing engaged with a free end of a gearing inputshaft for limiting axial movement of the torque converter.
 6. Thepowertrain of claim 1, further comprising: a second housing securedbetween the housing and the engine, including a wall which forms aboundary between a wet cavity in which the motor is located and a drycavity in which the torque converter is located, the wall defining anannular bore that supports a hub of the clutch.
 7. The powertrain ofclaim 1 wherein the drive shell is selectively rotatable independentlyfrom the torque converter.
 8. The powertrain of claim 1 wherein thetorsion damper includes a ring gear located at a radially outer locationof the damper, the ring gear configured to be engageable with a gear ofa starter motor.
 9. A vehicle powertrain, comprising: an engine; aclutch; a torque converter; a torsion damper connected to the engine andlocated between the engine and the torque converter; a transmissiongearing; a motor located between the torque converter and the gearing; adrive shell located between the damper and the clutch, partiallysurrounding the torque converter, and selectively rotatableindependently from the torque converter.
 10. The powertrain of claim 9wherein the torque converter is provided with an input shaft connectedbetween the motor and an impeller of the torque converter, a statormounted on a stator shaft fixed against rotation, and a turbine mountedon an input shaft of the transmission gearing.
 11. The powertrain ofclaim 10, wherein the torque converter includes the impeller, and asecond torsion damper located in an impeller shroud and in a power pathbetween the impeller and the input shaft of the transmission gearing.12. The powertrain of claim 10 wherein the input shaft of thetransmission gearing, the stator shaft, and the torque converter inputshaft are arranged coaxially.
 13. The powertrain of claim 9 wherein thetorque converter includes a thrust bearing engaged with a free end ofthe input shaft of the transmission gearing for limiting axial movementof the torque converter.
 14. The powertrain of claim 9, furthercomprising: a housing secured between a transmission housing and theengine, including a wall which forms a boundary between a wet cavity inwhich the motor is located and a dry cavity in which the torqueconverter is located, the wall defining an annular bore that supports ahub of the clutch.
 15. The powertrain of claim 9, further comprising: awet housing partially defining an enclosed wet cavity; and a dry housingadapted to be secured to the wet housing and to the engine, defining anenclosed dry cavity, the dry housing including a wall forming a boundarybetween the wet cavity and the dry cavity, the dry cavity containing thedrive shell and the torque converter.
 16. The powertrain of claim 9wherein the torque converter includes an impeller shroud and the driveshell partially surrounds the impeller shroud.
 17. The powertrain ofclaim 9 wherein the torsion damper includes a ring gear located at aradially outer location of the damper, the ring gear configured to beengageable with a gear of a starter motor.